1. Field of the Invention
This invention is related to wellbore section milling methods, section milling tools, and blades for such tools.
2. Description of Related Art
The prior art discloses various types of milling or cutting tools provided for cutting or milling a section of existing pipe or casing previously installed in a well. These tools have movable cutting blades and are lowered into the well or casing, the blades are deployed from the tool, and then the tool is rotated in a cutting operation. With certain tools, a suitable drilling fluid is pumped down a central bore of a tool for discharge beneath the cutting blades and an upward flow of the discharged fluid in the annulus outside the tool removes from the well cuttings or chips resulting from the cutting operation.
Milling tools have been used for removing a section of an existing tubular, e.g. casing from a well bore, to permit a sidetracking operation in directional drilling; in open hole gravel packing operations; to open a section for injection; and to provide a perforated production zone at a desired level.
Typically only a portion of a blade's milling surface actually mills the tubular during a milling operation and, as the portion is worn away, another portion of the blade commences milling. This can result in relatively extended time period for completing milling of a desired section of casing.
There has long been a need for efficient and effective section milling methods and a section mill useful in such methods. There had long been a need for a section mill blade with increased milling capability. There has long been a need for a mill that covers a coupling's total width for life of the blade.